Journal of Geological Society of India (Online archive from Vol 1 to Vol 78)

N. J. Pawar ¹, V. S. Kale ¹, T. C. Atkinson ², P. J. Rowe ²

Affiliations
1 School of Environmental Sciences, Dept. of Geography, University of Poona, Pune-411 007, IN
2 School of Environmental Sciences, University of East Anglia, Norwich, GB

Abstract

Waterfall tufa occurring in the semi-arid parts of the Upland Maharashtra has been dated by employing uranium series disequilibrium dating method. The dates correlate well with other evit1lences and suggest a wet climate during the genesis of the tufa.

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N. J. Pawar ¹

Affiliations
1 Department of Geology, University of Poona, Pune - 411007, IN

Abstract

The geochemistry of ground waters in the basaltic aquifers is considerably modified by the incongruent dissolution of augite and plagioclase from basalts. The analyses of the water chemistry data by using the WATSPEC aqueous-model computer programme for computing the ionic species abundances, the partial pressures of CO₂ (PCO₂) and mineral Saturation Indices (SIc and SId) suggest. that the ground waters are supersaturated with respect to calcite and dolomite. The modeling has indicated a state of equilibrium with respect to dolomite first followed by calcite. This state of equilibrium can be linked with the selective dissolution of augite leading to Mg-rich alkaline environment. which is also favourable for the formation of montmorillonite clays. The clays in turn act as a buffer and as a result the levels of Ca and Na do not exceed 1.8 mmol/L concentration. Due to the early dolomite saturation the Ca/Mg ratios areless than unity, whereas Na/Ca ratios are above unity suggesting precipitation of calcite and possibility of input from zeolites and mixing of difierent sources of water with local ground water.

The precipitation of calcite is under high PCO₂ conditions related to degassing and diffusion of CO₂ at the water-table and along cracks, joints and fissures in the basalts. The high PCO₂, dissolved oxygen content, presence of contaminants and fluctuations in the water table suggest that the ground water has chemically evolved under open system conditions.

Keywords

Geochemistry, Hydrogeology, Basalt Aquifers, Carbonate.

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N. J. Pawar ¹, J. D. Nikumbh ¹

Affiliations
1 Department of Geology, University of Pune, Pune - 411 007, IN

Abstract

Studies carried out on trace element geochemistry of groundwater from Behedi basin have shown spatial as well as temporal variations. While the spatial variations have been attributed to land use practices in the basin, the temporal changes indicated input of trace elements from soil zone due to rain-fed recharge. On the basis of spatio-temporal variations, weathering of rocks and human activity have been identified as the potential sources of trace elements in the groundwater. The budgeting of trace elements in the groundwater suggests that the rate of flushing of Cu is highest from the vadose zone to phreatic zone followed by Fe, Zn, Mn, Pb and toxic trace elements like Hg and As.

Keywords

Groundwater, Geochemistry, Trace Elements, Maharashtra.

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